Processes of preparing higher fatty aldehydes



Patented Jan. 31, 1939 PATENT OFFICE PROCESSES or PREPARING HIGHER FATTYALDEHYDES Anderson W. Ralston and Robert J. Vander Wal, Chicago, Ill.,asslgnors to Armour and Company, Chicago, 111., a corporation ofIllinois No Drawing. Application August 26, 1936,

Serial No. 98,087

13 Claims.

This invention relates to processes of preparing higher fatty aldehydesand it comprises processes wherein a metal soap or salt, such as alkalimetal salts, alkaline earth metal salts, zinc salts, copper salts, andthe like, of higher fatty acids, are reacted with formaldehyde; itfurther comprises processes wherein such soaps or salts are reacted withformaldehyde in the presence of steam, and, if desired, in the presenceof catalysts of an oxidizing nature such as metal oxides of the fifthand sixth groups of the periodic system.

In the United States patent, Number'2,033,539, in the names of Ralstonand Jackson, there are described processes of preparing higher fattyaldehydes' from higher fatty acids by reacting such fatty acids, whilein vapor phase, with formaldehyde in the presence of oxidizingcatalysts. That process is a marked step forward in the art since by itfatty acids or esters thereof can be directly converted to theircorresponding aldehydes. Before the discovery of this method there was'no' process available which could be used" commercially for-theconversion of the higher fatty acids to aldehydes. The classicalreaction between a calcium soap and calcium formate is of no commercialsignificance when dealing with higher fatty acids. These fatty acids areallphatic carboxylic acids having at least six carbon atoms and areacids commonly found in fats and fatty oils. Although the calciumformate reaction will'work fairly well with low molecular weight fattyacids, for example butyric or propionic, it is useless when dealing withthe higher fatty acids which react sluggishly and yield variousby-products and decomposition products as the result of side reactions.

The patented process referred to above overcomes many of thedisadvantages observed in the calcium formate method and permits higherfatty aldehydes to be prepared at low cost and in high yields. As aresult, these aldehydes have become available commercially and from themmany valuable organic materials can be prepared. For example, thealdehydes can be reduced to alcohols and the alcohols then sulfonat-edto form valuable wetting-out agents. The aldehyde group is extremelyreactive Since it is, in the higher fatty aldehydes, attached to rela--tively heavy alkyl radicals. these aldehydes offer ways of introducinsuch alkyl radicals into chemical compounds. Hitherto ways of alkylatingso that the introduced alkyl group was of relatively high molecularweight have been limited to a very few methods of doubtful valuecommercially.

of oxidizing catalysts.

The said patented process requires that the higher fatty acid (or itsester) be vaporized and contacted with formaldehyde at a rather highreaction temperature, generally about 400 C., and at least above .theboiling point of the fatty materials under the prevailing pressureconditions. The patented process also requires the presence Under theseconditions there is, of course, some tendency for the fatty acid todecompose to give tars, lower aldehydes, 10 and other by-productsgenerally of no use. When carefully controlled the process works verywell,. but, being vapor phase throughout, that is to say, all reactants(other than catalyst) are in the vapor condition, there are technicaldifficulties which are not associated with liquid or solid phasereactions.

Consequently we have set ourselves to the problem of developing a way ofconverting higher fatty acids to their corresponding aldehydes whichavoids a vapor phase reaction. And we have discovered that fatty acidsoaps derived from the higher fatty acids can be made to react withformaldehyde vapor. This means that we can'react the solid soaps withvaporous formaldehyde at a moderately elevated temperature and condensea liquid consisting largely of an aldehyde corresponding to the fattyacid of the 'soap treated. In the process of the present invention thereaction temperature can be much below the boiling point of the fattyacid from which the metal soap is made. Consequentlythe present processavoids any thermal conditions which might lead to cracking" the fattyacid with the resultant formation of tars and other undesirableby-products. Moreover no catalyst is necessary, although we do not wishto exclude a catalyst. Under some conditions, as when dealing with fattyacid soaps which seem to resist conversion to aldehydes at reasonablylow tem- 40 peratures (generally 200 to 300 C.) a small amount of anoxidation metal oxide catalyst can be admixed with the soap beforetreating with formaldehyde. Suitable catalysts are those described inthe aforementioned Ralston and Jackson patent. These are metal oxides ofthe fifth and-sixth groups, such as manganese oxide, vanadiurn oxide,chromium oxide, molybdenum oxide etc. Manganese oxide, however, is anoxide of a metal in the seventh group and forms an exception to the rulethat those oxides of metals in the fifth and sixth group are'best.Various mixtures of oxides can be used and generally the amount admixedwith the soap is very small; one percent is usually sufficient.

In the present process we find it advantageous to have steam presentalong with the formaldehyde vapor. lhis helps to steam-distill thealdehyde vapors formed by reaction between the metal soap and theformaldehyde. Consequently any tendency for the higher fatty aldehydevapors to decompose is avoided by this expedient. Steam can be omittedif desired, but little or no extra expense is involved in including it.-Perhaps the cheapest source of formaldehyde is the ordinary aqueoussolution thereof available commercially. 'Hence, when we boil thissolution to liberate formaldehyde therefrom we form quantities of watervapor at the same time and the mixture of water vapor and formaldehydeis advantageously led directly: into contact with the soap. 1

All of the soaps which we treat with formaldehyde are, of course,normally solid. Hence they can be supported in layers in a reactionvessel and formaldehyde vapor passed through the layers. Or a tower canbe loosely filled with the soap admixed with an inert porous materiallike pumice to expose large surface areas to contact with theformaldehyde. Some of the soaps, such as the alkali metal soaps may tendto liquify during the reaction, especially if much water be present.This is not to be regarded as a disadvantage since the formaldehyde willreact readily with the. liquid soap. Likewise the soaps of many fattyacids. such as oleic, are liquids at moclerately elevated temperatures,and in this case. our process can be considered a mixed liquid andvaporphase reaction. But only the formaldehyde (and steam when present)is a vaporous reactant; i

In substance then, our invention comprises processes of reacting soapswith formaldehyde.

' The reaction can be written schematically as follows, assuming that acalcium soap is used:

RCOOCaCOOR+HCHO- 2RCHO+CaCO3 Obviously the reaction is probably muchmore complex than the simple statement given above but the reactionexpresses the beginning and 'end products. Any steam present during thereaction appears to have no effect other than aiding in the vaporizationand distillation of the aldehyde. When alkali metal soaps are used thereaction can be written as follows:

Advantageously an excess of formaldehyde over that required by theoryis' used. 7

Before describing our invention with reference to the treatment ofspecific soaps we shall indicate its breadth. Our process is applicableto the conversion of all soaps derived from higher fatty acids. Byhigher fatty acids we mean those fatty soaps of alkali-forming metalsare operative.

These comprise soaps of sodium, potassium, cal- Of the many soapsaieasoi calcium since the fatty acids can be readily converted tocalcium soaps by treatment with lime. Consequently we find it moreadvantageous to use calcium soaps and we shall describe our inventionwith specific reference to the treatment of these soaps.

same when treating stearates, palmitates, myristates and other salts ofhigher fatty acids.

For example, we charge a suitable reaction vessel with 100 parts byweight of calcium laurate and heat the contents to a temperature of 200to 300 C. Generally about 275 C. will be found about the best. Then wevaporize 3000 parts by weight of a commercial formalin solutionconsisting of percent formaldehyde and 60 pencentwater and pass thesevapors into the reaction vessel.

Vapors leaving the reaction vessel are condensed. The condensateconsists of an aqueous layer composed of unreacted formalin and an oilylayer composed of lauraldehyde and any products of side reactions. Thisoily layer amounts to 40 parts by weight. Advantageously we wash it withwater, dissolve it in ether or other solvent which is immiscible withwater, extract the solvent solution with dilute caustic soda solution toremove any traces of acidic materials, remove the solvent, andfractionate the remaining oily layer. Most of the product islauraldehyde but it contains small quantities of methyl laurate andlaurone, a ketone.

Under similar conditionso-f temperature and quantities, sodium laurategives substantial yields of lauraldehyde, barium stearate givessubstantial yields of stearaldehyde and calcium palmitate yieldspalmitaldehyde. As the molecular weight of the fatty acid constituent ofthe soap decreases a moderate increase in side reactions is noted butthis can be corrected by operating at somewhat lower temperatures, about200 to 225 C. In any event it is advantageous to keep the reactiontemperature as low as possible consistent with reasonably rapid reactionvelocity.

Instead of using formalin solution we can, of course, use gaseousformaldehyde or formaldehyde-yielding materials such as meta andparaformaldehyde but inmost cases we prefer to use commercial formalinsince it is cheap and its water content, which vaporizes along with theformaldehyde, prevents the decomposition of the higher fatty aldehydesand aids in the rapid removal ofthem' from the reaction zone.

In the appended claims we use the language soap of a fatty acid havingat least six carbon atoms to denote the many soaps which we havedescribed. Likewise the term formaldehyde embraces formaldehyde presentduring the reaction regardless of its original source, be it formalin,0! meta or para formaldehyde, or other substances yielding formaldehydeat the reaction temperature.

Having thus described our invention what we claim is:

1. The process of preparing aldehydes which comprises passing gaseousformaldehyde into contact with a body of a soap of a fatty acid havingat least six carbon atoms, the soap being maintained at a moderatelyelevated temperature sufllciently high to induce reaction between theformaldehyde and the soap.

, the soap being maintained at a moderately elevated temperaturesufiiciently high to induce-reaction between the formaldehyde and thesoap.

3. The process of preparing aldehydes which comprises passing gaseousformaldehyde free of oxidizing gases into contact with a body of a soapof a fatty acid having at least six carbon atoms admixed with anoxidation catalyst, the soap being maintained at a moderately elevatedtemperature sufiiciently high to induce reaction between theformaldehyde and the soap, and oxidizing conditons being absent.

4. The process as in claim '1 wherein the soap is an alkali-formingmetal soap.

9. The process as in claim 3 wherein the soap is a calcium soap.

10. The process of preparing lauraldehyde which comprises passinggaseous formaldehyde into contact with a body of calcium lauratemaintained at a moderately elevated temperature to induce reactionbetween formaldehyde and the calcium laurate.

11. The process of preparing aldehydes which comprises passing gaseousformaldehyde into contact with a body of an alkali-forming metal soap ofa fatty acid having at least six carbon atoms, the soap being maintainedat a temper ture of about 200 C. to about 300 C.

12. The process of preparing aldehydes which comprises passing gaseousformaldehyde and Water vapor into contact with a body of analkali-forming metal soap of a fatty acid having at least six carbonatoms, the soap being maintained at a temperature of about 200 C. toabout 300 C.

- 13. The process of preparing aldehydes which comprises passing gaseousformaldehyde free of oxidizing gases and water vapor into contact with abody of an alkali-forming metal soap admixed with an oxidation catalyst,the soap being maintained at a temperature of about 200 C. to about 300C., and oxidizing conditions being absent.

ANDERSON W. RALSTON. ROBERT J. VANDER WAL.

